Specialized substrates for use in sequential lateral solidification processing

Abstract

Substrates having modified effective thermal conductivity for use in the sequential lateral solidification process are disclosed. In one arrangement, a substrate includes a glass base layer, a low conductivity layer formed adjacent to a surface of the base layer, a high conductivity layer formed adjacent to the low conductivity layer, a silicon compound layer formed adjacent to the high conductivity layer, and a silicon layer formed on the silicon compound layer. In an alternative arrangement, the substrate includes an internal subsurface melting layer which will act as a heat reservoir during subsequent sequential lateral solidification processing.

I claim:  
     
       1. A substrate having modified effective thermal conductivity for use in the sequential lateral solidification process, comprising: 
       (a) a base layer having a base layer conductivity and at least a top surface, said base layer comprising glass;  
       (b) a low conductivity layer having a conductivity which is less than said base layer conductivity, a first side and a second side, said low conductivity layer first side formed adjacent to said top surface of said base layer;  
       (c) a high conductivity layer having a conductivity which is greater than said base layer conductivity, a first side and a second side, said high conductivity layer first side formed adjacent to said second side of said low conductivity layer; and  
       (d) a semiconductor layer formed on said second side of said high conductivity layer.  
     
     
       2. The substrate of  claim 1 , wherein said low conductivity layer comprises porous glass. 
     
     
       3. The substrate of  claim 2 , wherein said low conductivity layer is in the range of 5,000 Angstroms to 2 microns thick. 
     
     
       4. The substrate of  claim 1 , wherein said high conductivity layer comprises a metal. 
     
     
       5. The substrate of  claim 4 , wherein said high conductivity layer is in the range of 50 to 5,000 Angstroms thick. 
     
     
       6. The substrate of  claim 1 , further comprising a silicon compound layer having a first side and a second side, wherein said silicon compound layer first side is formed adjacent to said second side of said high conductivity layer and said semiconductor layer is formed on said second side of said silicon compound layer. 
     
     
       7. The substrate of  claim 6 , wherein said silicon compound comprises silicon dioxide, and said silicon compound layer is sufficiently thick to prevent diffusion of impurities from said high conductivity layer. 
     
     
       8. The substrate of  claim 7 , wherein said silicon compound layer is in the range of 200 to 2,000 Angstroms thick. 
     
     
       9. A substrate having modified effective thermal conductivity for use in the sequential lateral solidification process, comprising: 
       (a) a base layer having a base layer conductivity and at least a top surface, said base layer comprising glass;  
       (b) a low conductivity layer having a conductivity which is less than said base layer conductivity, a first side and a second side, said low conductivity layer first side formed adjacent to said top surface of said base layer;  
       (c) a subsurface melting layer having a first side and a second side, said subsurface melting layer first side formed adjacent to said second side of said low conductivity layer;  
       (d) a silicon compound layer having a first side and a second side, said silicon compound layer first side formed adjacent to said second side of said subsurface melting layer; and  
       (e) a semiconductor layer formed on said second side of said silicon compound layer, wherein said subsurface melting layer is adapted to melt at a temperature which is less than or equal to a melting temperature of said semiconductor layer.  
     
     
       10. The substrate of  claim 9 , wherein said low conductivity layer comprises porous glass. 
     
     
       11. The substrate of  claim 10 , wherein said low conductivity layer is in the range of 5,000 Angstroms to 2 microns thick. 
     
     
       12. The substrate of  claim 9 , wherein said melting layer exhibits an increased conductivity after melting. 
     
     
       13. The substrate of  claim 9 , wherein said melting layer comprises a material having a high latent heat. 
     
     
       14. The substrate of  claim 13 , wherein said melting layer comprises Silicon Germanium. 
     
     
       15. The substrate of  claim 14 , wherein said melting layer is approximately 1000 Angstroms thick. 
     
     
       16. The substrate of  claim 9 , wherein said silicon compound comprises silicon dioxide, and said silicon compound layer is sufficiently thick to prevent diffusion of impurities from said melting layer. 
     
     
       17. The substrate of  claim 16 , wherein said silicon compound layer is in the range of 200 to 2,000 Angstroms thick.